COMPUTER GRAPHICS (XCS 354) UNIT – III

9. Define clipping? 

Clipping is the method of cutting a graphics display to neatly fit a predefined graphics region or the view port. 

10. What is covering (exterior clipping)? 

This is just opposite to clipping. This removes the lines coming inside the windows and displays the remaining. Covering is mainly used to make labels on the complex pictures. 

11. What is the need of homogeneous coordinates? 

To perform more than one transformation at a time, use homogeneous coordinates or matrixes. They reduce unwanted calculations intermediate steps saves time and memory and produce a sequence of transformations. 

12. Distinguish between uniform scaling and differential scaling? 

When the scaling factors sx and sy are assigned to the same value, a uniform scaling is produced that maintains relative object proportions. Unequal values for sx and sy result in a differential scaling that is often used in design application. 

13. What is fixed point scaling? 

The location of a scaled object can be controlled by a position called the fixed point that is to remain unchanged after the scaling transformation. 

14. Define Affine transformation? 

A coordinate transformation of the form X= axxx +axyy+bx, y ’ayxx+ayy y+by is called a two-dimensional affine transformation. Each of the transformed coordinates x ‘ and y ‘ is a linear function of the original coordinates x and y , and parameters aij and bk are constants determined by the transformation type. 

15. Distinguish between bitBlt and pixBlt? 

Raster functions that manipulate rectangular pixel arrays are generally referred to as raster ops. Moving a block of pixels from one location to another is also called a block transfer of pixel values. On a bilevel system, this operation is called a bitBlt (bit-block transfer), on multilevel system t is called pixBlt. 

16. List out the various Text clipping? 

• All-or-none string clipping -if all of the string is inside a clip window, keep it otherwise discards. 
• All-or-none character clipping – discard only those characters that are not completely inside the window. Any character that either overlaps or is outside a window boundary is clipped. 
• Individual characters – if an individual character overlaps a clip window boundary, clip off the parts of the character that are outside the window.